Portable electrical products typically use an underencapsulant for attachment of electrical elements to circuit boards as a mechanism to enhance assembly reliability. Studies have shown that under-encapsulant can improve solder joint reliability by a factor of 5 to 10 times.
Thermoset-based encapsulants have been widely used due to their thermal polymeric crosslinking stability, lower coefficients of thermal expansion, high bonding strength, and prior-curing flow characteristics at low temperatures. However, a major liability of thermoset-based encapsulants is their poor re-workability. That is, once the under-encapsulant is cured, there is no easy way to remove it.
Alternatives such as chemical etching and mechanical detaching are not viable for DCA (Direct Chip Attachment) applications since these processes tend to damage the die and/or the substrate.
Thus, there is a need for a method and DCA assembly that provides reworkability without damaging a die or a substrate.